Uniform impression typing mechanism



Dec. 21, 1954 F. BECKER 2,697,502

UNIFORM IMPRESSION TYPING MECHANISM Filed nec. 15, 1951 f2 M f5 ll INVENTOR. FRED BECKER fz. BY

A TTORNEV United States Patent O UNIFORM IMPRESSION TYPING MECHANISM Fred Becker, Queens Village, N. Y., assigner to Underwood Corporation, New York, N. Y., a corporation of Delaware Application December 15, 1951, Serial No. 261,783

19 Claims. (Cl. 197-17) This invention relates to typewriters having type carriers bearing different case types, and more particularly to imprint force control for obtaining uniform-shade impressions from all types, whether they be of small or large printing area or whether they be of upper case or lower case order.

Most commercial typewriters embody a plurality of selectively operable type carriers having each an upper and a lower case type. Since each type carrier has a plurality of types, there can be fewer of them and consequently they can be accommodated in a reasonably small space. Also the number of necessary parts in the machine is less. The different case types on many of the type carriers necessarily have printing faces of considerably differing area, and it thus follows that if type carriers embodying different case `types of different printing area are operated with equal force, the impressions made by such types will differ considerably in shade or vigor of appearance. In typewriters actuated by manual power imparted to the keys an experienced and good typist will give the key a lighter operating stroke whenever a small face character is typed, thereby `to cause it to type in the appropriate shade, but in work done by the average operator the small area characters are usually typed too heavily. The typed matter has thus not only an uneven appearance but some of the small face types will cut the paper.

In power operated typewriters the individual type bars are conventionally given the same operating stroke for typing by either case types, and to make the work look more presentable, the power actuating mechanism for the individual type carriers is usually adjusted so that the large face `type will type too lightly, thereby to cut down the strength of impression of the small face type. Obviously, such power typewriters do not produce the desirable uniform-shade impressions. Power typewriters also exist in which the keyboard has been modified to some extent to place upper and lower case types of more equal printing areas on the same type carriers. However, for mechanical complications it is not practical to apply this treatment to more than a few type actions, and, moreover, it necessitates special character arrangements in the keyboard, and thus specialized training for the operator.

lt is therefore a general object of the invention to provide an eliicient typewriter of the kind embodying upper and lower case types on common type carriers, which without the operator giving special operating attention will produce uniform-shade imprints from all types whether they be of lower or upper case order and of differing printing area.

It is a further object of the invention to provide an efficient typewriter in satisfaction of the above noted object and additionally to provide for ellicient regulation of the machine predeterminedly to type in the desired shade, uniformly by all types.

An object is also to control individually with respect to two different area types on a single type carrier, the force with which the type carrier strikes, in order that typing by the two diierent area types will be of even shade.

A more specific object of the invention is to provide individually in connection with one or more type carriers having two different case types of materially diiferent printing areas, devices under case-shift mechanism control, which will weaken the operation of'the type carrier if tyyping is eiiected by that case type which has the smaller printing area.

An additional object of the invention 1s to provide an ice eficient power-operated typewriter which produces irnprlnts of substantially uniform shade from all types, whether the types be of lower or upper case order and of small or large printing area.

A further object of the invention is to provide an eilicient power-operated typewriter, which will not only produce uniform-shade imprints from upper and lower case types of different printing areas, but which is also adapted to be regulated predeterminedly to produce uniform-shade impressions of desired vigor.

Still further objects and features will be in part obvious and in part pointed out particularly as the following description of the invention proceeds.

Referring now to the drawings:

Figure l is a sectional side elevation of a power typing mechanism of conventional construction, having associated therewith the mechanism of the invention to obtain uniform-shade printing impressions,

Figure 2 is a side elevation showing some of the parts seen in Figure l, and particularly showing a type action in the process of operation for typing in upper case, and straining an operation-weakening device,

Figure 3 shows in front elevation the right half of a conventional type bar rest, including downreaching brackets for support of operation-weakening devices,

Figure 4 shows an eccentrically mounted collar for an operation-weakening device,

Figure 5 is a fractional side elevation similar to Figure 2, illustrating a type action in the process of operation for typing by its lower case type, and straining an operationweakening device,

Figure 6 is a View similar to Figure 3 but the type bar rest has associated therewith a single bracket of modied structure for serving the operation-weakening devices of many type actions,

Figure 7 is a plan View illustrating an eccentrically mounted shaft and an impression regulating control thereon.

yThe invention is embodied in the well-known Underwood All Electric typewriter, the typing mechanism of which is disclosed in the patent to Yaeger, No. 2,254,764,

dated September 2, 1941. This typing mechanism comprises a usual complement of type bars or carriers 10 mounted on a segment 11 and individually swingable from diversive positions in front of a platen to type thereagainst at a common typing point 13. As each type carrier 10 approaches printing position it enters a usual type guide 15 which reaches upwardly from the segment 11. The type carriers 10 rest normally in closely adjacent relation radially in a usual arcuate type carrier rest 16 embodying a cushion indicated at 17. Each type carrier bears a lower case type 20 and an upper case type 21.

Normally the segment 11 is in the position seen in Figure 1 and the lower case type 20 of any actuated type carrier 10 will strike at the printing point 13. When it is desired to type by the upper case types 21 the segment 11 is shifted down to a position in which the upper case types 21 will type at the typing point 13. For such downward shift, the segment 11 is supported on a case-shift frame 22 which at each lateral side of the segment near the top is guided by a ball-and-raceway association indicated at 23 and which at the bottom is guided by a pivotally mounted bail 24 having two spaced arms 2S to which the case-shift frame 22 is articulated. Conventional mechanism, not shown, is provided to case-shift the frame 22 and therefore the segment 11. The arcuate type carrier rest 16 is supported at opposite ends on studs 27, see Figure 3, which in a manner not shown project forwardly from case-shift frame 22. It will be seen that the case-shift frame 22, the segment 11, the type carrier rest 16 and the studs 27 comprise a unitary case-shiftable structure. The type Vcarriers 10 are adapted to be selectively operated under This power element extends across the machine and is continuously power driven in the direction of the indicated arrow when the machine is in use. Said actuators 32 at their front ends are pivotally connected to arms 34, and springs 37 bias them rearwardy and upwardly so that their rear ends bear normally upwardly against a stationary bar 36 and so that their snatch elements 32a stand clear of the toothed power shaft 33. The various arms 34 are pivotally carried on a common, frame-supported pivot rod 35, and are individually associated for rolling contact with sub-levers 40 which are pivotally carried on a common, frame-supported pivot rod 41. The sub-levers 40 are of graded lengths to reach to appropriate levels for connection by wire links 42 to the related type carriers 1G. Operation of any type key 31 results in the lowering of the related actuator 32 into toothed motion receiving contact with the power shaft or member 33, and there ensues then a forward actuation of the actuator 32. The resultant forward swinging motion given to the arm 34, through the rolling contact between such arm and the related sublever 40, operates the latter forwardly and through the link 42 actuates the related type carrier 16. In the manner disclosed in said patent to Yaeger the rolling contact between the arms 34 and the sub-levers 40 is of a motion accelerating nature, and so individualized that despite the differing lengths of the levers 40, all the type carriers 16 are driven at substantially similar leverage conditions. The links 42 not only serve to transmit operating movements to the type carriers 10, but provide properly arranged articulated connections to permit case-shifting of the unit supporting the type carrier system. At a desired point in the power movement of any operated type carrier 16 toward the platen 14, a cam face 44 on the underside of the operated actuator 32 engages an individual abutment 47 to force the actuator out of engagement with the toothed power shaft 33. The point in the printing stroke of the type carrier 16 at which this happens is variable but in any case the actual power operation of the type carrier ceases appreciably before typing takes place. The type carrier, however, under the force of the momentum stored therein and the operating parts leading thereto, completes its typing movement. Such movement of each type carrier under the force of momentum toward printing position is against the power of a type action restoring spring 46 associated with the related sub-lever 40. Therefore, after each actual power stroke ends, the spring 46 will have an operation-weakening effect on the type carrier 10, the magnitude of which is greater if the divorcement of the actuator 32 from the power element 33 is early, and is lesser if the divorcement occurs late.

To predetermine desirable-length power strokes of the actuators 32 for the various type actions and thereby to regulate the typing force of the various type actions, the stated abutments 47 are provided on individually adjustable screws 50. These screws are on a common bar 51 which extends transversely of the machine. If any screw 50 is adjusted upwardly, the motion receiving engagement of the related power actuator 32 will be shortened. Downward adjustment of any screw 50 will predetermine a lengthened motion receiving engagement. Obviously, the nearer the type carrier is power actuated toward the printing point, the higher it will have been accelerated and the lesser the movement weakening effect of the type action restoring spring 46 will be.

For predeterminedly lengthening or shortening the motion receiving engagement of all actuators concomitantly, the bar 51 with all its abutments 47 is adjustable respectively upwardly and downwardly. To this end the bar 51 is part of a pivotally mounted bail structure comprising at each end of the bar 51, rigid therewith, a lever 52, these levers being pivotally carried at widely spaced points on the pivot rod 41. Each of the levers 52 has on a forwardly reaching arm a roller 53 bearing against a spiral cam 54. The latter are both fast on a shaft S5 which is turnably mounted in the opposite end walls of the machine. Springs 57 having opposite anchorage on the levers 52 and the machine frame urge the bail structure 51, S2 clockwise in reference to Figure l to the limit controlled by the spiral cams 54. The shaft 5S has fast thereon at its right end a knurled regulator wheel 5S which if turned clockwise with reference to Figure l will by action of the spiral cams 54 on the rollers 53 adjust the bail bar 51 upwardly, thereby to shorten predeterminedly the power strokes of all actuators 32. Opposite turning of the regulator wheel 58 will lower the bar 51 for predetermining longer power strokes of the actuators. Stop lugs 59 on one of the spiral cams 54- limit, in cooperation with the associated roller 53, the turning of the shaft 55 to a half turn. The wheel 58 has indices, not shown, to set it appropriately by reference thereto. A spring pressed detent, not shown, contacts the knurled surface of the wheel 58 to keep it normally from turning.

The mechanism described to this point does not provide for individualized impressions with respect to upper and lower case types of different printing area on the same type carriers. To provide for such individualized impressions, certain type actions embodying an upper and a lower case type of considerably differing printing areas have individual operation-weakening devices associated therewith. These devices are in the form of torsion springs 60 and are so controlled by the case-shift mechanism that each will have only an operation-weakening effect in respect to typing by that case type which has the smaller printing area. Each torsion spring 60 consists of a coiled portion 61, from which there extends one spring leg having a rearwardly pointed wire-formed nose 62, and from which there extends also another spring leg which ends in a partial ring 66. Said nose is locatable either in an upper or a lower perforation 63 provided in a bracket 64 individual to the particular type action, see

Figure 3. The brackets 64 related to the different type actions may be of appropriate forms as seen in Figure 3, all designed for securement, as at 65, to the underside of the type bar rest 16. The partial ring 66 of each spring 60 is dirnensioned to be clipped onto an eccentric collar 68 into a circumferential groove 67 thereof. The various collars 68 are mounted on the shaft 55 at appropriate locations by screws 69, see Figure 4, and the opposite legs of the torsion springs 60 are under tension to spread, wherefore the noses 62 bear with tension rearwardly. The partial rings 66 of the springs 60 permit pivotal displacement of the springs 60 about the collars 68 when the brackets 64 with the spring noses 62 therein caseshift along with the type bar rest 16. If the operating stroke for a type action is required to be weak in the downwardly shifted position of the type system, that is, for typing by an upper case type 21, then the spring element 60 is assembled in the machine to give the nose 62 a location in the upper perforation 63. During actuation -of the type action a protuberance 70 on the sub-lever 40 will encounter the spring nose 62 only if the type system is in lowered, upper case position, as is illustrated in Figure 2. lf a spring nose 62 is given a location in the upper perforation 63, then the protuberance 70 will miss the spring nose 62 if the type action is operated while the type system is located in the normal, lower case position seen in Figure l.

Should the lower case type 20 on a type carrier be smaller than the upper case type 21, then the spring nose 62 is placed in the lower perforation 63 of the bracket 64 and 'the protuberance 70 on the sub-lever 40 will then only strike the nose 62 and ex the spring 60 if the type system is in upper position for typing by the lower case type. The spring wire of which the spring 60 is formed ends at the nose 62 in a bent end which bears normally lirnitedly against the front side of the bracket 64. To condition the springs 60 for the appropriate operationweakening effect, the brackets 64 are bendable fore-andaft. If a bracket is bent farther rearwardly its associated spring 60 will be strained through a greater distance and conversely if a bracket is bent forwardly its associated spring will be strained through a lesser distance. Springs y60 are only required in connection with those type carriers which have case types of considerably differing printing area. Their operation-weakening effect may be said to supplement-the operation-weakening effect of the type action restoring springs 46.

It has been stated that the extents of power strokes impartable to the actuators 32 are predeterminedly variable for'all type actions -collectively by the regulator wheel 58. It follows that if the impressions of the small and `large face types are to be of the same shade for each particular setting given to the regulator wheel 58, then the operation-weakening resistance of the springs 60 must be varied in an appropriate relation to the settings made. In other words a setting of the regulator wheel 58 for a shorter operation of the type carrier 10 calls for a weak ened resistance of the spring 60, and vice versa, a setting for a longer power actuation of the type carrier 10 vcalls for a strongeroperation-weakening resistance.

It has been stated that the ring-ends 66 of the springs 60 are associated with eccentrically mounted collars 68 on the shaft 55. The position and degree of eccentricity on the shaft is correlated to the cams 54 so that if the regulator wheel 58 is given a setting for a shorter actuator stroke, all the springs 60 will be relaxed proportionately for the noses 62 thereof to offer appropriately less operation-weakening resistance. The eccentricity of the collars and the strength of the springs is properly chosen so that for any setting of the regulator wheel S the different area types on the same type carriers will give impressions of equal shade.

In Figure 3 individual brackets 64 give support to the spring noses 62. In Figure 6 a modified structure is shown wherein a row of independently bendable tabs 74 are provided on a single cross member 75. The member 75 is caused to partake in the case-shift movements of the type system by being secured at 76 to the lowermost part of the type bar rest 16 and by having also at each lateral side, at 77, a bracket connection with said type bar rest. The various tabs 74 are bendable similarly to the brackets 64 for increasing or decreasing the operation-weakening eiect of the spring 60. The structure shown in Figure 6 is preferable if many of the type carriers require diifering strength impressions for their lower and upper case types.

In Figure 4 the regulator shaft 55 is shown equipped with a spring supporting collar 68 of which there may be as many as required. If many type carriers are to strike with differing force for upper or lower case types then the modified structure shown in Figure 7 is preferable. In said Figure 7 the collars 68 are integrated into a single eccentrically mounted shaft 78 which has circular grooves 80 for association of the springs 60 therewith. The shaft 78 carries at each end one of the cams 54 and has fast thereon an impression regulator wheel 58. Eccentricity of mounting is provided for by pointed screws 81 supported on opposite side walls of the machine.

The protuberances 70 are preferably in the form of plates attachable by screws 73 to the desired sub-levers 40, all the sub-levers 40 being provided with screw holes. It will be noted from Figures 2 and 5, that the spring operating faces of said protuberances 70 which encounter the spring noses 62 in lower case typing, have a different slant than the spring operating faces which encounter the spring noses in upper case typing. These respectively different slants are provided to permit the case-shift movements to be concluded while an operated type action is approaching operated position, said slant faces allowing the sDring noses 62 to glide into operative relation with the protuberances.

From the foregoing it will be evident that the typewriter of the invention produces, without any attention by the operator, even-shade impressions from all types, whether they be of small or large-face printing area or whether typing is done by one or another case type on the same type carrier. Furthermore, the machine can be regulated to predetermine, according to desire, the shade of impression the machine will produce, and the regulated shade of impressions will always be substantially uniform.

While the invention has been shown and described with reference to the details shown in the drawings, it is t o be understood that it is susceptible of modification and change and comprehends other constructions and details, without departing from the spirit and scope it represents.

What is claimed is:

1. In a typewriter having a plurality of individually actuatable type actions embodying each a type carrier having a lower and an upper case type, the combination with a case-shift mechanism movable to occupy one or another case-shift position, of operation-weakening means individually associated with each type action, and means under control of said case-shift mechanism to cause at least one of said type actions to be subjected to a stronger inuence of its operation-weakening means when said case-shift mechanism is in said one position than when it is in said other position, and to cause at least another of said type actions to be subjected to a stronger inuence of its operation-weakening means when said case-shift mechanism is in the said other position than when it is in the said one position.

2. In a typewriter having a plurality of individually actuatable type actions embodying each a type carrier having a lower and an upper case type, the combination with case-shift mechanism movable to one or another position, of an operation-weakening spring device for each one of said type actions, and means controlled by said caseshift mechanism to render some of said devices operable by the said type actions only when said mechanism is moved to said one position, and to render the other of said devices operable by said type actions only when said mechanism is moved to said other position.

3. The invention set forth in claim 2, and means to adjust the effectiveness of each spring device individually.

4. The invention set forth in claim 2, and means to adjust the effectiveness of said spring devices collectively.

5. In a typewriter having a plurality of type actions embodying each a type carrier having a lower and an upper case type, means to power-actuate said type actions selectively toward printing positions, and short thereof, said type actions completing their typing movements by accumulated momentum, a case-shift mechanism movable to occupy one or another position to control selectively typing by said upper or said lower case types, resilient means individual to each of said type actions strainable thereby during their momentum movements to printing position for weakening their typing movements, means controlled by said case-shift mechanism to incapacitate some of said resilient means whenever said mechanism is moved to one position and to incapacitate other of said resilient means whenever said mechanism is moved to the other position, and means to adjust the individual resilient means for varied movement weakening effect.

6. In a typewriter having a plurality of type actions embodying each a type carrier having a lower and an upper case type, means to power-actuate said type actions selectively toward printing positions, and short thereof, said type actions completing their typing movements by accumulated momentum, a case-shift mechanism movable to occupy one or another position to control selectively typing by said upper or said lower case types, indivdual operation-weakening devices associated with said type actions for operation thereby during their momentum movements to printing position, and means controlled by said case-shift mechanism to incapacitate some of said devices whenever said mechanism is moved to one position and to incapacitate other of said devices whenever said mechanism is moved to the other position.

7. In a typewriter having a plurality of type actions embodying each a type carrier having a lower and an upper case type, means to power-actuate said type actions selectively toward printing positions, a case-shift mechanism movable to occupy one or another position to control selectively typing by said upper or said lower case types, an operation-weakening device associated with a type action for operation thereby, means controlled by said case-shift mechanism to incapacitate said device whenever said mechanism is moved to one of said positions, regulating means, including a control, to regulate predeterminedly the power actuating means to diminish or increase the typing impact of the type actions, and

means operatively associated with said regulating means and said device to diminish or to increase the operationweakening capacity of said device respectively as the regulating means is adjusted respectively to diminish or to increase the typing impact of the type actions.

8. In a typewriter having a plurality of type actions embodying each a type carrier having a lower and an upper case type, means to power-actuate said type actions selectively, a case-shift mechanism movable to occupy one or another position to control so that said type carriers may type by said lower or said upper case types, individual operation-weakening devices associated with said type actions for operation thereby, means controlled by said case-shift mechanism to incapacitate some of said devices whenever said mechanism is moved to one position and to incapacitate other of said devices whenever said mechanism is moved to the other position, means including a control, to regulate prcdeterminedly the power-actuating means to diminish or to increase the typing impact of the type actions, and means operatively associated with said regulating means and said devices to diminish or to increase the operation-weakening capacity of said devices respectively as' the regulating means is adjusted respectively` to diminish or to increase the typing impact of the type actions.

9. In a typewriter having a plurality of type actions embodyingveach a type carrier having a lower and an upper casetype, means to power-actuate said type tlc-- tions selectively, case-shift means movable to occupy one or another position so that said type carriers may type by said lower or said upper case types, operationweakening means operable by said type actions, means controlled by said case-shift mechanism to incapacitate said operation-weakening means with reference to said type actions whenever said mechanism is moved to one of its positions, means, including a control, to regulate predeterminedly the power-actuating means to diminish or to increase the typing impact of the type actions, and means operatively associated with said regulating means and said operation-weakening means to diminish or increase the operation-weakening capacity of the latter respectively as the regulating means is adjusted respectively to diminish or increase the typing impact of the type actions.

10. ln a typewriter having a plurality of type actions embodying each a type carrier having a lower and an upper case type, power means to impart operating strokes to said type actions selectively comprising, a motor-operated power member common to said type actions, a power actuator for each type action selectively connectable with said power member to receive a type action operating motion, and means to disconnect said power actuators from said power member automatically after partial operations of the type actions to type, each operated type action concluding its typing movement by momentum stored therein, a case-shift mechanism movable to occupy one or another position for selectively controlling typing by said upper or said lower case types. individual operation-weakening means associated with and operable by said type actions', means controlled by said case-shift mechanism to incapacitate certain of said operation-weakening means by movement of said caseshift mechanism from said one to said other position, and to incapacitate certain of said operation-weakening means by movement of said mechanism from said other to said one position, an impression regulating control, and means to adjust said disconnecting means and said operation-weakening means conjointly by said impression regulating control.

11. The invention set forth in claim l0, said disconnecting means including means to adjust it with respect to each actuator individually, and means for adjusting each operation-weakening means individually.

12. In a typewriter having a plurality of type actions embodying each a type carrier having a lower and an upper case type, means to power-actuate said type actions selectively toward printing positions, a case-shift mechanism movable to occupy one or another position to control selectively typing by said lower or said upper case types, resilient devices individual to said type actions and each strainable by the operation of the related type action to weaken its typing force, means individual to said devices to adjust their weakening effect, means controlled by said case-shift mechanism to shift said devices for some to be strainable only in one case-.shift position of said mechanism and for others to be strainable only in the other case-shift position of said mechanism, means to regulate the power-actuating means for varied power effect on said type actions, means including a member common to all said resilient devices and movably mounted to regulate their operation-weakening effect, and means to regulate both said regulating means conjointly.

13. In a typewriter having a plurality of individually actuatable type actions embodying each a type carrier, at least one type action embodying a type carrier comprising two different case types of which one has a relatively large printing area and of which the other has a relatively small printing area, the combination with a case-shift mechanism movable to occupy one or another position to line up one or the other of Asaid types for typing, of operation-weakening means individual to said one type action and comprising an operation-weakening resilient element, and means responsive to movement of the case-shift mechanism and directly in control of said operation-weakening means, to condition `the latter for weaker eilect if the large printing area type is lined 11p for typing, and to condition it for a Vstronger etect if the small printing area type is lined up for typing.

14. The invention set forth in claim 13, and means to regulate the effectiveness of said operation-weakening means in respect to typing by the small printing `area 8 type without affecting it in respect to typing by the large printing area type.

15. 1n a power-operated typewriter having a plurality of type actions embodying each two different case types of which one has a relatively large printing area and of which the other has a relatively small printing area, and comprising each an actuator element connectable transitorily to a power member for power operation of the type action toward printing position, the movement to print being completed by momentum, the combination with a case-shift mechanism movable to occupy one or another case-shift position to line up one or the other case type of each type action for typing at a printing point, of an individual operation-weakening device associated directly with each of said type actions, and means responsive to movement of said case-shift mechanism and directly controlling the individual operation-weakening devices to have in reference to each individual type action a stronger effect if typing is effected in the position of said mechanism in which the small printing area type will print than when typing is elected in the position of said mechanism in which the large printing area type will print.

16. In a typewriter having two individually actuatable type actions embodying each a type carrier having a lower and an upper case type, the combination with a case-shift mechanism movable to occupy one or another case-shift position, of an individual operation-weakening spring means directly associated with each of said type actions, and means to control the two operation-weakening spring means by said case-shift mechanism for one in one case-shift position of said mechanism to offer more resistance to the operation of its related type action and for the other in the other case-shift position of said mechanism to offer more resistance.

17. The invention set forth in claim 16, and means individual to each said spring means to regulate the resistance offered thereby in the case-shift position of .said mechanism in which it Oilers more resistance.

18. In a typewriter having a type action embodying a type carrier having a lower and an upper case type, means to power actuate said type action toward printing position, the printing movement being completed by power of momentum, a case-shift mechanism movable to one or another position to control selectively typing by said different case types, operation-weakening means associated with said type action, means to control said operation-weakening means by said case-shift mechanism to have a stronger operation-weakening effect in one of the two case-shift positions of said mechanism, means .to

regulate said power actuating means for varied power effect on the type action, and means controlled by said regulating means to regulate the operation-weakening means for varied effect in at least the case-shift position of said mechanism in which it has a stronger operationweakening effect.

19. In a power-operated typewriter having a type action embodying two different case types and comprising an actuator element connectable transitorily to a power member for power operation of `the type action toward printing position, the printing movement being completed by momentum, the combination with a case-shift mechanism movable to occupy one or another case-shift position to line up one or the other of said types for typing at a printing point, of operation-weakening spring means associated with said type action, means under control of said case-shift mechanism to lend said spring means greater operation-weakening capacity in one position of the case-shift mechanism than in the other position, a regulator to predetermine the extent to which said type action is power-operable toward printing position by said actuator element, and means controlled by said regulator to vary in respect to the said one position of said mechanism the operation-weakening capacity of said spring means in asense so that for longer and shorter power operations of the .type action the spring resistance is respectively `increased and decreased.

References Cited in the le ,of this patent UNITED STATES PATENTS 

